Method for extracting lead-212 and bismuth-212 from thorium-232 decay chain

Abstract

The present invention relates to the field of preparation of medical radioisotopes, and specifically relates to a method for extracting lead-212 and bismuth-212 from a thorium-232 decay chain, comprising: enabling a solution containing a thorium-232 decay chain substance to pass through an anion exchange resin column, wherein the solution containing the thorium-232 decay chain substance contains halogen ions, and the concentration of protons in the solution containing the thorium-232 decay chain substance is greater than 0.01 mol / L, lead-212 and bismuth-212 are adsorbed by the anion exchange resin column, while other nuclides directly pass through the anion exchange resin column and are not adsorbed; introducing a leaching reagent to desorb lead-212 and bismuth-212 from the anion exchange resin column; and performing separation extraction to obtain lead-212 and bismuth-212. In the present invention, lead-212 and bismuth-212 can be extracted simultaneously, the extraction speed is fast, the purity is high, and organic pollution of a product is not easily caused.

Description

Methods for extracting lead-212 and bismuth-212 from the thorium-232 decay chain Technical Field

[0001] This invention belongs to the field of medical radioactive isotope preparation, specifically relating to a method for extracting lead-212 and bismuth-212 from the decay chain of thorium-232. Background Technology

[0002] In recent years, the global incidence of cancer has been rising year by year, and cancer has become a serious threat to human life and health. Medical radioactive isotopes have important applications in cancer diagnosis and treatment, and are of great significance for ensuring people's health and social stability. 212 Pb / 212 Bi is one of the few radioisotopes that can be used in targeted alpha therapy (TAT), and it has shown good efficacy in treating malignant tumors such as ovarian cancer, pancreatic cancer, prostate cancer, and breast cancer. However, its resources are extremely scarce, leading to... 212 The development and clinical application of Pb (lead)-targeting drugs are severely limited.

[0003] 212 Pb / 212 Bi is 232 The decay products of Th were isolated and extracted from natural thorium. 212 Pb / 212 Bi has the potential to fundamentally solve global problems. 212 Pb / 212 The bottleneck problem of insufficient Bi supply is due to the fact that it does not require a reactor or accelerator, but relies solely on... 232 The spontaneous decay of Th can yield a sufficient amount 212 Pb / 212 Bi. 232 The Th decay chain is shown in Figure 1.

[0004] Extracted from natural thorium 212 Pb / 212 Bi can be separated into direct and indirect methods. The direct separation method refers to the selective extraction of thorium directly from natural thorium using highly selective adsorption materials. 212 Pb and 212 Bi is for medical use; while indirect separation refers to first from 232 Th separation 228 Ra, and then separated step by step. 228 Th、 224 Ra, ultimately through 224 Ra / 212 Pb generator obtains 212 Pb / 212 Bi. Currently, indirect separation methods are frequently reported, and the technology is relatively mature. (Using...)224 Ra / 212 Pb generator for 212 Pb / 212 Bi (with a half-life of 10.6 h) is advantageous for large-scale distribution and transportation. However, this method also has drawbacks, namely, the separation steps are numerous and complex, requiring multiple waiting periods for daughter product growth and repeated purification and testing of the separated products. This increases the risk of radiation hazards to personnel (especially since short-lived radioactive gases are involved in the process). 220 The lack of Rn protection also leads to high production costs and long production cycles.

[0005] In comparison, the direct separation method is simple and efficient, making it highly suitable for city and county-level operations, and even provincial-level operations. 212 Pb / 212 Bi is centrally distributed for supply. However, the difficulty and key to this method lies in finding suitable separation materials and technologies to enable... 212 Pb and 212 Bi selectively from 232 It can be efficiently separated from the Th decay chain. Currently, there are reports in the literature that crown ether extractants can be used for selective separation from natural thorium based on solid-phase adsorption (i.e., using Pb resin). 212 The target of Pb, but it cannot be extracted simultaneously. 212 Bi, resulting in the waste of scarce radionuclide resources. In addition, crown ether extractants are very expensive and have a certain degree of water solubility, and may require further separation and purification to remove dissolved crown ethers before being made into drugs. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a method for extracting lead-212 and bismuth-212 from the thorium-232 decay chain, which can simultaneously extract lead-212 and bismuth-212, and the extraction speed is fast, the purity is high, and it is not easy to cause organic pollution to the product.

[0007] This invention provides a method for extracting lead-212 and bismuth-212 from the thorium-232 decay chain. A solution containing thorium-232 decay chain substances is passed through an anion exchange resin column. The solution contains halide ions, and the concentration of hydrogen ions in the solution is greater than 0.01 mol / L (preferably 0.5–2 mol / L). Lead-212 and bismuth-212 are adsorbed by the anion exchange resin column, while other nuclides such as 228Ra, 228Ac, and 232Th pass directly through the column without adsorption. An eluent is then introduced to desorb lead-212 and bismuth-212 from the anion exchange resin column, thus separating and extracting lead-212 and bismuth-212.

[0008] The thorium-232 decay chain includes parent 232 Th, and each level of decay daughter such as 228 Ra, 228 Ac, 228 Th, 212 Pb, 212 Bi, 208 Tl, and the like, as shown in Fig. 1.

[0009] Preferably, the concentration of halogen ions in the solution containing thorium-232 decay chain material is 0.3-4 mol / L, more preferably 0.5-2 mol / L.

[0010] Preferably, the thorium-232 decay chain material is a thorium salt or a thorium oxide, more preferably a soluble salt containing thorium-232.

[0011] Preferably, the thorium salt is thorium nitrate hydrate.

[0012] Preferably, the halogen ions are present in the form of an acid or a salt containing Cl - , Br - , or I - , preferably a hydrochloric acid, a hydrobromic acid, or a hydroiodic acid, preferably at a concentration of 0.3-4 mol / L, more preferably 0.3-2 mol / L. More preferably, the acid is a hydrobromic acid or a hydroiodic acid.

[0013] In the solution containing thorium-232 decay chain material, the anions other than the halogen ions cannot be present at a concentration exceeding that of the halogen ions, otherwise competitive adsorption will occur, resulting in poor selectivity of adsorption of lead and bismuth.

[0014] When a hydrochloric acid is used, the concentration of the hydrochloric acid is preferably 0.5-3 mol / L, more preferably 1-2 mol / L.

[0015] When a hydrobromic acid is used, the concentration of the hydrobromic acid is preferably 0.3-2 mol / L, more preferably 0.3-1 mol / L.

[0016] When a hydroiodic acid is used, the concentration of the hydroiodic acid is preferably 0.5-3 mol / L, more preferably 0.5-1 mol / L.

[0017] Preferably, the anion exchange resin is a silicon-based anion exchange resin.

[0018] Preferably, the silicon-based anion exchange resin is prepared by in-situ solution copolymerization of 4-vinylpyridine and divinylbenzene in the presence of a initiator and a diluent in the pores of porous SiO2, to obtain a silicon-based polyvinylpyridine, and methylating the silicon-based polyvinylpyridine with dimethyl sulfate, to obtain the silicon-based anion exchange resin.

[0019] The initiator is a mixture of azobisisobutyronitrile and 1,1'-azobis(cyclohexanecarbonitrile), and the diluent is phenylacetone and diethyl phthalate. The volume ratio of 4-vinylpyridine to divinylbenzene is 15-20:5-7.

[0020] The solvent for the methylation reaction is a methanol aqueous solution, and the mass ratio of methanol to water is 1:1.

[0021] Preferably, the effective particle size of the silicon-based anion exchange resin is 37-150 μm, the BET specific surface area is 50-80 m 2 / g, and the average pore size is 10-50 nm.

[0022] Preferably, when separating lead-212, the elution reagent is an aqueous solution with a salt concentration or an acid concentration less than 0.5 mol / L, and more preferably ultrapure water; when separating bismuth-212, the elution reagent is a nitric acid solution with a concentration greater than 0.5 mol / L, and more preferably 1-2 mol / L HNO3.

[0023] Preferably, before the elution reagent is introduced, a solution containing halogen ions (preferably hydrochloric acid, hydrobromic acid, or hydroiodic acid, and the concentration is preferably 0.5-1 mol / L) is introduced to elute other ions except lead-212 and bismuth-212.

[0024] The present application has the advantages that the present application provides a technical method for directly, rapidly, and selectively separating 232 Pb and 212 Bi from natural 212 Th through a large number of experimental researches. The present application preferably uses a silicon-based anion exchange resin. Compared with conventional all-organic commercial resins, the silicon-based anion exchange resin has the advantages of fast adsorption / desorption speed, low column pressure, and good hydrodynamic performance, and is especially suitable for efficient separation and extraction of radioisotopes with short half-lives, such as 212 Pb (half-life 10.64 h) and 212 Bi (half-life about 1 h). It is found in experiments that the silicon-based anion exchange resin has high adsorption selectivity for 212 Pb and 212 Bi in a halogen medium, and does not substantially adsorb other nuclides in the 232 Th decay chain. Therefore, the separation method using the silicon-based anion exchange resin can effectively solve the many defects in the traditional method of separating and extracting 212 Pb using crown ether materials. The method can not only be applied to selectively separating and extracting 232 Pb and 212 Bi from natural 212 Th decay chain, 228 Ra decay chain, 228 Th decay chain, and224 Selective separation and extraction from Ra decay chain 212 Pb and 212 Bi can also be applied to any other situation involving the selective extraction of lead and bismuth from complex systems such as thorium, radium, actinium, lanthanum, barium, lead, and bismuth.

[0025] This invention provides a method that can be derived from 232 Direct, rapid, and selective separation in Th solutions 212 Pb and 212 Bi's novel method effectively avoids the use of expensive and water-soluble crown ether extractants. Experimental gamma spectroscopy confirmed the obtained... 212 The Pb sample has very high purity and is basically free of impurity nuclides such as Th, Ac, and Ra.

[0026] The material used in this invention is a silicon-based anion exchange resin, which has the advantages of low cost, fast adsorption / desorption kinetics, low column pressure, good hydraulic properties, and chemical stability and non-dissolution. Furthermore, it can simultaneously achieve… 232 In the Th decay chain 212 Pb and 212 The separation and extraction of Bi ensures the maximum utilization of scarce nuclide resources.

[0027] This invention utilizes an acidic solution containing halide ions, which enables the anion exchange resin to simultaneously and rapidly adsorb ions. 212 Pb and 212 Bi is present, but it does not adsorb other metal elements. During elution, different eluents can be used to achieve the desired effect. 212 Pb and 212 Bi elution, thereby achieving 212 Pb and 212 Bi is separated, and the separated product has high purity. Attached Figure Description

[0028] Figure 1 is 232 Th and 232 The decay chain of U.

[0029] Figure 2 shows a comparison of the adsorption kinetics of SiPyR-N4 resin with commercial anion exchange resins IRA900 and PA316.

[0030] Figure 3 shows the change of TOC content in SiPyR-N4 suspension over time.

[0031] Figure 4 shows the static adsorption behavior of SiPyR-N4 resin for different metal ions in hydrochloric acid medium.

[0032] Figure 5 shows the static adsorption behavior of SiPyR-N4 resin for different metal ions in hydrobromic acid medium.

[0033] Figure 6 is the static adsorption behavior of SiPyR-N4 resin for different metal ions in hydroiodic acid medium.

[0034] Figure 7 is the static adsorption behavior of SiPyR-N4 resin for different metal ions in nitric acid medium.

[0035] Figure 8 is the static adsorption behavior of commercial IRA900 resin for different metal ions in hydrochloric acid medium.

[0036] Figure 9 is the static adsorption behavior of commercial PA316 resin for different metal ions in hydrochloric acid medium.

[0037] Figure 10 is the comparison of the elution effect of different eluents on lead.

[0038] Figure 11 is the comparison of the elution effect of different eluents on bismuth.

[0039] Figure 12 is the separation of Pb, Bi from Th, La and Ba; wherein I: dead volume; II: mixed metal solution; III: 1.0 M HC1 solution; IV: ultrapure water; V: 1.0 M HNO3.

[0040] Figure 13 is the solid 232 Th(a) and the separated 212 Pb(b) and 212 Bi(c) sample gamma spectrum comparison, wherein (a) is the gamma spectrum of solid 232 Th, (b) is the gamma spectrum of the separated 212 Pb solution, and (c) is the gamma spectrum of the separated 212 Bi solution. DETAILED DESCRIPTION

[0041] Example 1 The anion exchange resin is a silicon-based anion exchange resin, which is prepared in two steps. First step: synthesis of silicon-based polytetraethenylpyridine (SiPyR-N3). First, 100 g of porous Si02particles are added to the flask of a rotary evaporator. The flask is kept rotating at low speed. The rotary evaporator is purged twice with nitrogen, and then vacuumed to 20 hPa. At the same time, 45 mL of ACP (acetophenone), 30 mL of DEP (diethyl phthalate), 17.69 mL of 4-vinylpyridine, 6.41 mL of DVB (divinylbenzene), 0.3215 g of AIBN (azobisisobutyronitrile), and 0.2144 g of V-40 (1,1'-azobis(cyclohexanecarbonitrile)) are sequentially mixed. After the initiators AIBN and V-40 are completely dissolved, the mixed oil phase is introduced into the flask of the rotary evaporator using a pressure difference. The rotation speed is adjusted and the flask wall is gently tapped to mix the oil phase and Si02thoroughly until no obvious clumps are formed, at which point it is considered that the oil phase has completely entered the Si02. Nitrogen is charged to restore atmospheric pressure, and then the temperature is raised to start the polymerization reaction. An oil bath is used for heating, and the temperature is maintained at 60 °C for 1 h, 70 °C for 2 h, 80 °C for 2 h, and 90 °C for 13 h. After the reaction is completed, the product is washed twice alternately with acetone and ultrapure water. The product is named SiPyR-N3 and is dried in a vacuum drying oven at 40 °C for 48 h before use.

[0042] Second step: preparation of silicon-based anion exchange resin SiPyR-N4 using SiPyR-N3 as a precursor. An appropriate amount of SiPyR-N3 resin and 500 g of methanol / water (mass ratio of 1:1) are sequentially added to a dry 250 mL three-necked flask equipped with a stirring paddle and a dropping funnel. The reaction temperature is maintained at about 25 °C using a water bath. Then, 3 times the molar amount of dimethyl sulfate contained in the vinylpyridine of the SiPyR-N3 resin in the flask is measured, and the solution is slowly added to the flask using a dropping funnel. The solution is stirred at low speed, and the pH value is controlled at neutral using 10 M sodium hydroxide solution. When the pH of the solution gradually stabilizes and no longer changes, 2 times the molar amount of dimethyl sulfate contained in the vinylpyridine of the SiPyR-N3 resin in the flask is added. The pH value is continuously controlled, and the reaction is maintained under neutral conditions. After the reaction is completed, the product is named SiPyR-N4 and is washed with acetone and ultrapure water alternately for two times each. Then, the SiPyR-N4 is further washed with 5 M NaCl solution and ultrapure water to convert it to the chloride type. Finally, the converted SiPyR-N4 is placed in a vacuum drying oven at 40 °C for 48 h before use.

[0043] The quaternized strong basic silicon-based anion exchange resin SiPyR-N4 has a functional group of 1-methylpyridine, an effective particle size of 37-150 μm, an organic content of about 25.5%, a BET specific surface area of about 52.2 m2 / g, and a total pore volume of about 0.45 mL / g. 2 / g, and the average pore size was 36.8 nm.

[0044] Example 2: Comparative experiment of adsorption speed of different resins, the steps are as follows: (1) a certain amount of bismuth nitrate was dissolved in 1.0M HCl medium to obtain a mixed working solution containing 1.0M HCl and 500mg / L Bi.

[0045] (2) some clean glass bottles with a volume of 40mL were taken, 0.05g of the resin of example 1 was added to each glass bottle. Then 20mL of the mixed working solution was taken and added to the above glass bottle. The lid was sealed and placed in a 25℃ water bath shaker for oscillation, and the oscillation frequency was 120rpm.

[0046] (3) different mixing contact times were set, and as soon as the time node was reached, the sample was immediately separated by microporous filter membrane.

[0047] (4) the solutions before and after adsorption were diluted to an appropriate concentration with dilute nitric acid, and then the concentration of Bi in the solution was measured by inductively coupled plasma atomic emission spectrometer (ICP-AES). The adsorption efficiency of the resin was determined based on the difference between the concentrations before and after adsorption, and the adsorption kinetics curve of the adsorption efficiency changing with time was drawn.

[0048] (5) the adsorption kinetics curves of commercial strong basic anion exchange resins IRA900 and PA316 were also evaluated by the above steps (1)-(4), and the adsorption speed was compared.

[0049] IRA900 resin is a commercial strong basic anion exchange resin produced by Dow Chemical Company, USA, and its backbone structure is styrene-divinylbenzene copolymer, and the functional group is trimethyl quaternary amine salt.

[0050] PA316 resin is a commercial strong basic anion exchange resin produced by Mitsubishi Resin Company, Japan, and its backbone structure and functional group are the same as those of IRA900 resin.

[0051] The experimental results are shown in Figure 2, the resin of example 1 basically reached adsorption equilibrium within 10min, while IRA900 and PA316 resins needed more than 120min to reach adsorption equilibrium. The adsorption speed of the resin of example 1 was significantly faster than that of the commercial anion exchange resin.

[0052] Example 3: Chemical stability experiment of the resin of example 1, the steps are as follows: (1) a batch of clean glass bottles were taken, 0.1g of the resin of example 1 was added to each glass bottle, then 30mL of 1.0M HCl solution was taken and mixed with the resin and sealed with a lid.

[0053] (2) Place the batch of glass bottles in a 25°C constant temperature water bath shaker and oscillate them at a frequency of 120 rpm.

[0054] (3) Set different mixing contact times, and after the time point is reached, immediately separate the sample with a microporous filter membrane for solid-liquid separation.

[0055] (4) The total organic carbon (TOC) content in the solution was analyzed using a total organic carbon (TOC) analyzer, and the TOC change curve with contact time was plotted.

[0056] The experimental results are shown in Figure 3. The TOC content in the solution did not change significantly with time, proving that the resin in Example 1 has good chemical stability and is insoluble in water.

[0057] Example 4 Selective adsorption experiment, the steps are as follows: (1) Weigh a certain amount of thorium nitrate, lead nitrate, bismuth nitrate, lanthanum nitrate and barium nitrate, dissolve them in HCl media of different concentrations, and prepare a mixed solution containing 100 mg / L Th, 90 mg / L Pb, 90 mg / L Bi, 60 mg / L La and 60 mg / L Ba.

[0058] (2) Take some clean 40mL small glass bottles, add 0.05g of the resin from Example 1 to each bottle, and then add 20mL of the mixed solution to each small glass bottle. Seal the bottles and place them in a 25°C water bath shaker at a shaking frequency of 120rpm. Here, the stability... 207 Pb is used to simulate 232 In the Th decay chain 212 Pb; stable 209 Bi is used to simulate 232 In the Th decay chain 212 Bi and La have similar chemical properties to Ac and are used to simulate... 232 In the Th decay chain 228 Ac; Ba has similar chemical properties to Ra, and is used to simulate 232 In the Th decay chain 224 Ra and 228 Ra.

[0059] (3) After shaking for 2 hours, the sample was separated into solid and liquid by using a microporous filter membrane.

[0060] (4) The solutions before and after adsorption were diluted with dilute nitric acid to a suitable concentration, and then the concentration of each metal element in the solution was measured using inductively coupled plasma atomic emission spectrometry (ICP-AES). The adsorption efficiency of the resin for different metal elements was determined based on the difference in concentration of each metal element before and after adsorption.

[0061] (5) Take the above (1-4) steps to investigate the adsorption behavior of SiPyR-N4 resin in hydrobromic acid and hydroiodic acid medium.

[0062] The experimental results are shown in Figures 4, 5 and 6, and the resin of Example 1 shows unique adsorption selectivity for Pb and Bi in the three acid media, and does not adsorb Th, Ba and La elements.

[0063] As can be seen from Figures 4-6, in static adsorption, the anion exchange resin mainly adsorbs Bi in hydrochloric acid medium, and also adsorbs a small amount of Pb, and basically does not adsorb other ions such as La, Th and Ba. In hydrobromic acid medium, the resin mainly adsorbs Bi and Pb, but the adsorption effect is better in low concentration hydrobromic acid than in high concentration hydrobromic acid, and when the concentration exceeds 3 mol / L, the adsorption effect of the resin on Bi and Pb will decrease. The resin also mainly adsorbs Bi and Pb in hydroiodic acid medium, and the adsorption effect of the resin in low concentration hydroiodic acid is better than in high concentration hydroiodic acid, and when the concentration exceeds 2 mol / L, the adsorption of the resin on Bi and Pb will decrease.

[0064] Comparative Example 1 and Example 4 differ in that step (1) is: weigh a certain amount of thorium nitrate, lead nitrate, bismuth nitrate, lanthanum nitrate and barium nitrate, and dissolve them in different concentration HNO3 medium. The same as Example 4.

[0065] The experimental results are shown in Figure 7, and the silicon-based anion exchange resin basically does not adsorb any kind of metal ion in HNO3 medium, which means that selective separation of lead and bismuth cannot be achieved. It can be seen that Example 4 is more suitable for selective separation of lead and bismuth in the solution system than Comparative Example 1.

[0066] Example 5 is a comparative experiment of the adsorption behavior of different anion exchange resins in hydrochloric acid medium for thorium, lead, bismuth, lanthanum and barium, and the steps are: (1) weigh a certain amount of thorium nitrate, lead nitrate, bismuth nitrate, lanthanum nitrate and barium nitrate, and dissolve them in different concentration HCl medium to obtain a mixed solution containing 100 mg / L Th, 90 mg / L Pb, 90 mg / L Bi, 60 mg / L La and 60 mg / L Ba.

[0067] (2) Take some clean small glass bottles with a volume of 40 mL, add 0.05 g of IRA900 resin to each glass bottle, and then take 20 mL of the mixed solution and add it to the small glass bottle. Seal with a lid and place it in a 25°C water bath shaker for shaking, with a shaking frequency of 120 rpm.

[0068] (3) After 2 hours of shaking, the sample is subjected to solid-liquid separation with a microporous filter membrane.

[0069] (4) The solutions before and after adsorption were diluted to a suitable concentration with dilute nitric acid, and then the concentration of each metal element in the solution was measured by inductively coupled plasma atomic emission spectrometer (ICP-AES). The adsorption efficiency of the resin for different metal elements was determined based on the difference between the concentrations of each metal element before and after adsorption.

[0070] (5) The adsorption behavior of IRA900 resin and PA316 resin in hydrochloric acid medium was also investigated by the above steps (1-4), and was compared with the adsorption behavior of SiPyP-N4 for the above metal elements.

[0071] The experimental results are shown in Figures 8 and 9. The anion exchange resins produced by three different companies all have the same adsorption behavior, i.e. they can selectively adsorb lead and bismuth under experimental conditions, and thus can be used for the selective separation of lead and bismuth in the Th decay chain. 232 Th decay chain 212 Pb and 212 Bi.

[0072] Example 6: Lead elution experiment, the steps are as follows:

[0073] (2) The flow mode from bottom to top was adopted, and first, ultrapure water was passed to remove air bubbles, and the flow rate was adjusted to 1.0 mL / min.

[0074] (3) 50 mL of 1.0M HCl was passed to pretreat the resin column.

[0075] (4) A certain amount of lead nitrate was weighed and dissolved in 1.0M HCl medium to prepare a hydrochloric acid solution containing 90mg / L Pb.

[0076] (5) About 45 mL of the above lead solution was passed, and then 50 mL of ultrapure water was passed, and the concentration of lead in the effluent was measured by ICP-AES.

[0077] (6) The above steps (1-4) were repeated, and the ultrapure water in step (5) was replaced by 0.1M HCl and 0.01M HCl respectively, to compare the elution effect of ultrapure water and dilute acid solution on lead.

[0078] The experimental results are shown in Figure 10. Compared with 0.1M HCl and 0.01M HCl, ultrapure water can more easily elute lead, achieving a higher enrichment factor.

[0079] Example 7: Bismuth elution experiment, the steps are as follows:

[0080] (2) Adopting the mode of flowing from bottom to top, first pass in the ultrapure water to remove the bubbles, and adjust the flow rate to 1.0 mL / min.

[0081] (3) Pass in 50 mL of 1.0M HCl to pretreat the resin column.

[0082] (4) Weigh a certain amount of lead nitrate, dissolve it in 1.0M HCl medium, and prepare a hydrochloric acid solution containing 90mg / L Bi.

[0083] (5) Pass in about 45mL of the above Bi solution, and then pass in 100mL of 1.0M HNO3 solution, and measure the concentration of Bi in the effluent by ICP-AES.

[0084] (6) Repeat the above steps (1-4), and replace the ultrapure water in step (5) with 3M HNO3 and 0.1M HNO3 respectively, and compare the elution effect of 1.0M HNO3 and other concentrations of nitric acid solution on bismuth.

[0085] The experimental results are shown in Figure 11, compared with 3.0M HNO3 and 0.1M HNO3, 1.0M HNO3 can more easily elute Bi, and achieve higher enrichment factor. On the contrary, 0.1M HNO3 can hardly achieve complete elution of Bi.

[0086] Example 8 Cold-state simulation separation experiment, the steps are, (1) Take some resins of Example 1, fill them in a glass adsorption column with specifications φxh=5mmx50cm, until they are filled.

[0087] (2) Adopting the mode of flowing from bottom to top, first pass in the ultrapure water to remove the bubbles, and adjust the flow rate to 1.0 mL / min.

[0088] (3) Pass in 50 mL of 1.0M HCl to pretreat the resin column.

[0089] (4) Weigh a certain amount of thorium nitrate, lead nitrate, bismuth nitrate, lanthanum nitrate and barium nitrate, dissolve them in 1.0M HCl medium, and prepare a mixed solution containing 100mg / L Th, 90mg / L Pb, 90mg / L Bi, 60mg / L La and 60mg / L Ba.

[0090] (5) Pass in about 45mL of the above mixed solution, at this time Pb and Bi are fixed on the resin column at the same time, while other elements such as thorium, lanthanum and barium directly pass through the resin column.

[0091] (6) Pass in 15mL of 1.0M HCl solution to elute the residual thorium, lanthanum and barium on the resin column.

[0092] (7) Pass 25 mL of ultrapure water through to desorb the Pb adsorbed on the resin column.

[0093] (8) Pass 50 mL of 1.0 M HNO3 solution through the resin column to desorb the Bi fixed on the resin column.

[0094] (9) The effluent was collected using a fraction collector, with a collection time of 5 minutes per centrifuge tube. The concentration of each metal element in each centrifuge tube was measured using ICP-AES.

[0095] The experimental results are shown in Figure 12. The resin column of Example 1 can selectively immobilize Pb and Bi in the mixed metal solution, but it does not adsorb Th, Ba, and La elements. Pb and Bi were successfully separated from the Th solution and recovered separately.

[0096] Example 9 Hot separation experiment, the steps are as follows: (1) Take a certain amount of resin from Example 1 and fill it into a glass adsorption column with specifications of φ×h=5mm×50cm until it is full.

[0097] (2) Adopt the bottom-up flow mode, first introduce ultrapure water to remove air bubbles, and adjust the flow rate to 1.0 mL / min.

[0098] (3) Pretreatment of the resin column by introducing 50 mL of 1.0 M HCl.

[0099] (4) Weigh 2.0g of thorium hydrate and dissolve it in 45mL of 1.0M HCl medium.

[0100] (5) Pass about 45 mL of the above mixed solution into the resin column. At this time, Pb and Bi are simultaneously fixed on the resin column, while other elements such as thorium, actinium and radium pass directly through the resin column.

[0101] (6) Pass 15 mL of 1.0 M HCl solution through the resin column to wash off the residual thorium, actinium and radium.

[0102] (7) Pass 25 mL of ultrapure water through the resin column to remove the adsorbed ions. 212 Pb is desorbed.

[0103] (8) Pass 50 mL of 1.0 M HNO3 solution through the resin column to fix the... 212 Bi desorbed.

[0104] (9) Collect the collected data 212 Pb samples were subjected to gamma-ray spectral analysis and compared with... 232 The gamma spectrum of Th was compared. Simultaneously, ICP-AES analysis was performed. 212 Th concentration in Pb samples.

[0105] The experimental results are shown in Figure 13. Compared with the solid 232 The γ-spectrum peaks of Th obtained by the present application are 212 Pb and 212 The γ-spectrum peaks of Bi sample nuclides are less, 232 The trace amounts of Th present in the decay chain are 224 Ra and 228 Ac are completely removed, while 212 Pb and 212 Bi are substantially retained and have high purity. The ICP-AES measurement results show that, 212 Pb and 212 The concentration of Th in the Bi sample solution is 0 mg / L, which is lower than the instrument detection limit, proving that 232 Th and 228 Th are completely removed. Therefore, in combination with Example 4, the experiment successfully proves that the method can be used to directly extract 232 Pb and 212 Bi from the Th decay chain selectively. 212

[0106] It should be understood by those of ordinary skill in the art that the above discussion of any of the embodiments is merely exemplary and is not intended to suggest that the protection scope of the present application is limited to these examples; the above embodiments or technical features among different embodiments can also be combined, the steps can be implemented in any order, and there are many other changes of different aspects of one or more embodiments of the present application as described above. In order to be brief, they are not provided in details.

[0107] One or more embodiments of the present application are intended to cover all such alternatives, modifications and variations falling within the broad scope of the present application. Therefore, any omissions, modifications, equivalent replacements, improvements, etc. made in the spirit and principles of one or more embodiments of the present application should be included in the protection scope of the present application.​

Claims

1. A method for extracting lead-212 and bismuth-212 in thorium-232 decay chain, characterized in that, The solution containing thorium-232 decay chain substances is passed through an anion exchange resin column, the solution containing thorium-232 decay chain substances contains halogen ions, and the concentration of hydrogen ions in the solution containing thorium-232 decay chain substances is greater than 0.01 mol / L, lead-212 and bismuth-212 are adsorbed by the anion exchange resin column, and other nuclides directly pass through the anion exchange resin column without being adsorbed, lead-212 and bismuth-212 are desorbed from the anion exchange resin column by passing a leaching reagent, and lead-212 and bismuth-212 are separated and extracted.

2. The method of claim 1 wherein, The concentration of the halogen ions is 0.3-4 mol / L.

3. The method of claim 1 wherein, The thorium-232 decay chain substances are thorium salts or thorium oxides.

4. The method of claim 3 wherein, The thorium salt is hydrated thorium nitrate.

5. The method of claim 1 wherein, The halogen ions are present as acids or salts containing CI - , Br - or I - .

6. The method of any one of claims 1-5, wherein, The anion exchange resin is a silicon-based anion exchange resin.

7. The method of claim 6 wherein, The preparation method of the silicon-based anion exchange resin is that 4-vinylpyridine and divinylbenzene are subjected to in-situ solution copolymerization reaction in the pores of porous SiO2 in the presence of an initiator and a diluent to obtain silicon-based polyvinylpyridine, and the silicon-based polyvinylpyridine is subjected to methylation reaction with dimethyl sulfate to obtain the silicon-based anion exchange resin.

8. The method of claim 6 or 7, wherein, The effective particle size of the silicon-based anion exchange resin is 37-150 μm, the BET specific surface area is 50-80 m 2 / g, and the average pore size is 10-50 nm.

9. The method of any one of claims 1-5, wherein, When separating lead-212, the leaching reagent is an aqueous solution with a salt concentration or an acid concentration less than 0.5 mol / L; and when separating bismuth-212, the leaching reagent is a nitric acid solution with a concentration greater than 0.5 mol / L.

10. The method of claim 9 wherein, When separating lead-212, the leaching reagent is ultrapure water; and when separating bismuth-212, the leaching reagent is 1.0M nitric acid. When separating lead-212, the leaching reagent is ultrapure water; and when separating bismuth-212, the leaching reagent is 1.0M nitric acid.

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